As I understand it...

If Porsche had drilled a few holes in the intermediate shaft to let it "breathe" and to let any oil which entered the shaft be expelled like a centrifuge, would that have cured the problem which ultimately led to IMS failures?

The DOF does seem to make a whole lot of sense. But I am asking about the foundational design. If they had a way for air an oil to get out of the shaft, would the failures have occurred?

solved one more minor issue - the rancid oil that is trapped int he shaft itself, but would not have provided oil to the bearing, whcih sits at the end.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
JMstamford,ct
If Porsche had drilled a few holes in the intermediate shaft to let it "breathe" and to let any oil which entered the shaft be expelled like a centrifuge, would that have cured the problem which ultimately led to IMS failures?

The DOF does seem to make a whole lot of sense. But I am asking about the foundational design. If they had a way for air an oil to get out of the shaft, would the failures have occurred?

After reading Grant's comments about what he found in the tear-down, the holes in the IMS shaft also came to my mind. Getting that old oil out of there is a good idea w/o jeopardizing the strength of the shaft.

Removing he seals from the bearing would let the oil in the shaft drain.
A hole in the shaft would add to oil spay in the crank case, not necessarily a good thing.

Ed B

The LNE unit doesn't have them on either side.

The acrid oil remained



Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
The LNE unit doesn't have them on either side.

The acrid oil remained

Grant

The acrid oil could be because oil only gets splashed in. I think that's the big advantage of DOF. "Fresh" oil is fed into the bearing giving it better lubrication.

I am talking about the oil in the hollow IMS - the shaft

It has little incentive to migrate out at all

Grant

gee-lenahan-at-gee-mail-dot-com



Edited 1 time(s). Last edit at 01/15/2017 08:36PM by grant. (view changes)

The oil gets into the bearing and the shaft due to the expansion and contraction of the heated then colled air in the IMS tube. If there was a vent hole(s) in the tube, it could vent at a place other than through the bearing. Thus the vented IMS tube would cure issue number 1 which is oil being sucked through the seal and bearing. It would also allow any oil which did get into the tube to escape preventing the acid condition.

Bottom line, if the lifetime seals and grease could conceivably work but for the incursion of oil through the bearing, could not a simple vent in the shaft cure a tone of problems?

Its not just oil from the shaft. It sits bathed in oil until a) it spins and b) the motor sucks up oil from the sump.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

If you injected pressurized oil, then you wouldn't need the sealed, ball bearing element in the first place. A bearing that uses no balls but floats on a pressurized flow of oil is called a plain bearing. That is exactly what is on the other side of the IMS and has been since Porsche started using IMSs in the 60s.

While no one really knows why Porsche removed the plain bearing from one end of the IMS, it is strongly suspected this was done as a cost cutting measure.

Good thinking, but you just designed the original engines.

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[en.wikipedia.org]

Peace
Bruce in Philly